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Hello asyncio

#python   #asyncio  

Table of Content

Asyncio achieves concurrency through the use of coroutines. Coroutines are functions that can be paused and resumed at specific points during their execution. This allows multiple coroutines to run concurrently within a single thread.

When programming, asynchronous means that the action is requested/ schedule, although not performed at the time of the request. It is performed later.

  • coroutine is a function that can be suspended and resumed.

  • Future: A handle on an asynchronous function call allowing the status of the call to be checked and results to be retrieved.

  • Asynchronous Task: Used to refer to the aggregate of an asynchronous function call and resulting future

coroutine#

A coroutine is a regular function with the ability to pause and resume its execution

to mark function as coroutine we add the async keyword before def statement. To pause coroutine execution we use the await keyword.

async#

async mark function as coroutine coroutine execute on event loop there other asyncio method to register/schedule the coroutine on event loop

coroutine
async def hello() -> int:
    pass

co = hello()
print(co)

<coroutine object hello at 0x7f5058f6b530>
sys:1: RuntimeWarning: coroutine 'hello' was never awaited

await#

The await keyword pauses the execution of a coroutine

result = await my_coroutine()

The await keyword causes the my_coroutine() to execute, waits for the code to be completed, and returns a result.

asyncio app#

import asyncio
import logging

logging.basicConfig(format="[%(levelname)s] %(asctime)s %(message)s", level=logging.DEBUG)
log = logging.getLogger(__name__)

async def main():
    log.info("Starting coroutine")
    await asyncio.sleep(2)
    log.info("Coroutine finished")

asyncio.run(main())

The asyncio.run() function used to run a coroutine in an event loop. This function: - creates an event loop, - runs the coroutine in the event loop, - closes the event loop when the coroutine is complete.

Reference#